create react app Configuration file after build app

Create config.js or json file outside src directory and include it in index.html like

<script src="%PUBLIC_URL%/config.js" type="text/javascript"></script>

configure parameters in config.js

config.js

var BASE_URL = "http://YOUR-URL";

you can get paramenters like

const BASE_URL = window.BASE_URL;

You can store you JSON file in the public/ folder and it'll automatically provide this file when you host your Create React App.

Something like: /public/my-configuration-file.json

then when you restart your application:

localhost:3000/my-configuration-file.json

will provide you this json file.